WASHINGTON – Israel has only mere days to launch an attack on Iran’s Bushehr nuclear reactor if Russia makes good on its plan to deliver fuel there this weekend, former US ambassador to the UN John Bolton warned Tuesday.He said that once Russia has loaded the fuel into the reactor -- slated for Saturday – Israel would no longer be willing to strike for fear of triggering widespread radiation in an attack.RELATED:Iranian jet crashes near nuclear plantOdds of US strike on Iran could rise after Gates departure'Iran to build third plant'“This is a very, very big victory for Iran,” Bolton told The Jerusalem Post. “This is a huge threshold.”Bolton, who also once oversaw US non-proliferation policy, said that when Russia announced the plans to load the fuel last Friday, “the element of surprise was essentially taken away” from Israeli calculations.Bolton noted that he doesn’t “have a clue” as to whether Israel would actually attack, but he said, “If Israel was right to destroy the Osiraq reactor, is it right to allow this one to continue? You can’t have it both ways.”Israel took out Iraq’s Osiraq reactor during a stealth mission in 1981. It is also believed to have conducted a similar strike on an alleged Syria nuclear site in 2007.Russia signed a contract with Iran to construct the Bushehr reactor in 1995, but has several times delayed completion. In announcing the long-overdue fuel installation, which should make Bushehr operational in September, Russia did not indicate why it was going ahead with the final stages now. In addition to Bushehr -- for which Russia says it has guarantees it will receive back the spent fuel, the material needed to make a nuclear bomb -- Iran has its own uranium enrichment facilities.Iran expert Ilan Berman of the American Foreign Policy Council said that the uranium enrichment plants are the real backbone of Iranian efforts and expenditures to get a nuclear weapons capability, and he suspected that they, rather than Bushehr, would be Israel’s primary targets in any attack.He suggested that Bolton was setting up a “straw man” by focusing on the fuel delivery to the Bushehr reactor.“It’s not at all clear that Bushehr would be a high value target because it’s only tangentially related to any conceivable Iranian nuclear weapons program,” he said. “My suspicion is this isn’t a game changer. This isn’t going to give Iran enough fissile material for a bomb overnight.”Berman added that since Bushehr is the most public Iranian nuclear facility, and therefore well monitored by international inspectors, it was also a less likely candidate for use by Iran to construct a bomb, though he nevertheless said if it became operational it would be “an enormous PR coup for the Iranians.”Bolton dismissed the idea that international inspectors would contain the threat from the Bushehr reactor, pointing to instances inspectors had been kicked out.He also said it was unlikely that Israel would attack Bushehr now and make another sortie against the enrichment facilities in later months because that would be a much more challenging task. For one thing, he point out that an attack on Bushehr would likely spur the Russians to transfer to Iran advanced missile defense systems it has agreed to sell Tehran but refrained from actually delivering. Instead, Bolton indicated, if Israel were to attack now it would probably hit multiple targets.Iran, for its part, dismissed talk of a possible Israel strike.On Tuesday, Foreign Ministry spokesman Ramin Mehmanparast was quoted as saying that "these threats of attacks had become repetitive and lost their meaning." He also reportedly told correspondents in Tehran, "According to international law, installations which have real fuel cannot be attacked because of the humanitarian consequences.”The rhetoric comes as the US increased sanctions on Iran as part of its ongoing efforts to ratchet up pressure on Tehran.On Tuesday the US Treasury announced dozens of additional names of Iranian banks and individuals that fall under sanctions law.The Associated Press contributed to this report.